DAMASCUS, Syria—The Syrian military touted advances in the suburbs around Damascus on Sunday, after pounding areas targeted in an alleged chemical weapons attack last week with what residents called the heaviest shelling since the start of the civil war.
The military said that on the eastern outskirts of Damascus, it succeeded in recapturing a section of the Damascus-Homs highway from rebels that runs past the town of Zamalka.
It also reported killing an unspecified number of opposition fighters in ongoing clashes inside the adjacent district of Jobar and destroying rebel positions in Ein Tarma and Irbin, also in the eastern suburbs of the Syrian capital.
Syrian opposition groups have accused forces loyal to President Bashar al-Assad of attacking all four areas and another nearby opposition stronghold with chemical weapons on Wednesday as part of the regime's bid to oust rebels from strategic suburbs that ring the capital. Opposition groups allege that more than 1,000 people were killed in the alleged attacks, including fighters and civilians.
Doctors Without Borders said on Saturday that three opposition-run hospitals it supports in the eastern Damascus region reported receiving roughly 3,600 patients with "neurotoxic symptoms" within three hours on Wednesday morning. Of those, 355 died, the Paris-based humanitarian organization said.
The Syrian regime last week initially accused the opposition of fabricating claims of chemical weapons use in the Damascus suburbs as part of an effort to derail the mission of United Nations inspectors, who arrived in Syria more than a week ago to investigate previous incidents of alleged chemical weapons use elsewhere in the country.
But over the weekend, the regime said it had "definitive proof" that rebels used the substances in the suburbs in what it described as a gambit to thwart the military's current campaign.
The Syrian government agreed on Sunday to allow U.N. inspectors into some of the areas to investigate last week's suspected poison gas attack, and the U.N. said that field work would start Monday. But it wasn't clear how they will be able to accomplish this amid the continuing military campaign.
All of the areas have been sealed off by the military, which has imposed heavy restrictions at the two remaining checkpoints leading into a large swath of the eastern, rebel-controlled suburbs. The same applies to Moadhamiya, a town southwest of Damascus that the opposition says also was attacked with chemical weapons last week.
Concrete barriers and army checkpoints blocked the main entrance to Moadhamiya, while back roads winding through lush farmland and orchards were cut off with earthen berms that residents say were erected a day before the start of the current military campaign on Wednesday.
A man who lives on the edge of the town and has son fighting with rebels in adjacent Daraya said the bombardment of Moadhamiya by government forces on Wednesday was the worst the area has seen since the start of the conflict more than two years ago.
He said government forces pounded the town with a barrage of artillery and rockets for about 10 hours starting at 2 a.m. He smelled none of the odors associated with some chemical weapons, he said, but haze engulfed the entire area for about one hour. "It was the most savage time," the man said.
He said both Daraya and Moadhamiya are largely occupied by rebels now but several hundred civilians remain in each town. "Many people have lost hope and see their only comfort in death," he said.
As he spoke, explosions could be heard nearby every few minutes as artillery rounds and rockets bombarded Moadhamiya from surrounding hills.
A senior official with one of the U.N. humanitarian agencies operating in Syria said the government had rejected its repeated requests, including one last month, to visit Moadhamiya. He said the area had been off limits to them for more than eight months.
"We hear the situation is very dire," he said speaking at a hotel in central Damascus.
Write to Sam Dagher at sam.dagher@wsj.com
